Network calculating board



Sept. 1, 1953 G. w. BILLS 2,650,760

NETWORK CALCULATING BOARD Filed Feb. 1, 1950 GENERATOR FILTER INVENTOR. GLENN W. BILLS Patented Sept. 1, 1953 UNITED STATES FATENT OFFICE (Granted under Title 35, U. S. Code (1952),

sec. 266) 3 Claims.

The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment to me of any royalty thereon in accordance with the provisions of the act of March 3, 1883 (22 Stat. 625), as amended by the act of April 30, 1928 (45 Stat. 467, 35 U. S. C., 1946 Ed. Sec. 45).

This invention relates generally to calculating boards used for miniature representation of power transmission networks. There have been many such calculating boards which have included resistances, inductances and capacitances to represent transmission lines, and transformers, both fixed core and variable core to represent generators and motors. The present invention utilizes the same kind of connections for lines and loads as in the calculating boards now in use but in place of some of the conventional simulated generators, a novel combination with a circuit with special characteristics is used.

Conventional calculating boards are provided with a real generator supplying the board with power at some convenient frequency such as 400 cycles per second. The generators of the power system are simulated by machines commonly referred to as self-synchronous motors with a polyphase stator and single-phase rotor which operate as induction regulators or phase shifters. When these machines are all connected to the same real generator, which is usually a threephase machine, the polyphase, or primary, windings are all in phase due to interconnection. The single-phase, or secondary, windings are also interconnected through the simulated system network of lines and loads. Being thus interconnected, both through the primary and secondary windings, any change in phase angle between the two windings of the phase shifter changes the current flowing through the adjusted machine and also the currents through all other interconnected machines.

This defect could, theoretically, be remedied by using independent real generators each with independent prime movers in place of the phase shifters in the calculating board, but this solution would be prohibitively expensive. It is, however, of theoretical interest in that such a solution establishes an ideal criterion of operation with which the performance of other methods may be compared.

A principal object of my present invention is to produce a network calculating board in which a plurality of simulated generators can be independently adjusted to specified loads with the same degree of independence as with a plurality of independently driven real generators. Another object is to produce a calculating board in which a plurality of simulated generators can be to provide third and other generators.

What constitutes this invention is set forth in the specification following and the accompany-- ing drawing. and succinctly described in the ap-- pended claims.

The drawing is a simplified circuit diagram: illustrative of the principles of operation of this.

invention.

In the drawing, a conventional power system is;v represented by a network of resistances, I to 8 inelusive. Resistors I, 2 and 3 represent transmission lines between generators and other lines: 4 and 5, and loads 6, I and 8. These resistors, are generalized actually to include inductive and. capacitive reactances which, being well under-- stood in the prior art, are omitted from the draw-- ing for convenience.

A conventional real generator II is connected to the network through a regulating transformer: I2 which may be omitted if the voltage of gen erator I is suitable for direct connection.

A plurality of negative impedance networks I3; and M are connected into the network as if they were independent generators. The structural details and the characteristics of operation of negative impedance networks are well known. Networks suitable for use as components It and I4 are described by Brunetti and Greenough, page 542 of Proceeding of the Institute of Radio Engineers, for December 1942; also by E. L. Ginzton, page of Electronics, for July 1945; and are also described in a copending application for Patent Serial No. 83,281, Stabilized Negative Impedance Circuit by Halvor T. Strandrud, in which application has matured into Patent No. 2,557,154. From Strandruds patent, it will be apparent that each network I 3 and I 4 is provided independently with power which, being direct current, has no phase relationship to generator I I or to each other. The power supplies for networks I3 and I 4 are indicated by batteries I5, I6, I1, and I8. Each negative impedance network 3 as described by Strandrud includes, as illustrated by the network I3, two amplifiers 2i and 22 and a tuned filter circuit 23. Work M comprises amplifiers 2 and 25, and filter 25.

In the operation of this system, the simulated generator H, which is actually also a small real generator, provides the frequency control for the network calculating board network. The negative impedance networks is and i l do not generate a frequency but act as passive impedances which carry currents of the frequency of generator ii. The magnitudes of the currents carried by the negative impedances l3 and M are proportional to their terminal voltages and, inversely proportional to the magnitudes of the values of the impedances. The directions of the currents are the reverse of the currents carried by ordinary (positive) impedances connected to the system and so they appear as generators when viewed from the system point of View whereas ordinary impedances appear as loads.

The usual adjustments of system loads are made in the appropriate resistors of the board and in the simulated generators H, 13 and I4. Changes in the magnitude and distribution of the system load are made by variation of individual load and line resistors and by adjustment of individual simulated generators. The negative impedance networks, being independent of phase except through interconnection in the simulated line and load network, can be independently adjusted for load as Well as for power factor without changing the load and power iactor of the other negative impedances except insofar as there may be unadjusted changes in voltage. If, under these conditions, the total load of the system remains constant, the simulated generator H which, being a real generator, takes or drops load to compensate for the loads dropped or taken by the negative impedance under adjustment.

correspondingly, net- I claim:

1. In a network calculating board, the com bination of an alternating current generator pro viding power at a predetermined frequency, said generator being connected to a network of impedances representing lines and loads, said network of impedances also being connected to a plurality of negative impedance networks simulating real generators, said negative impedance networks being controlled in frequency by said alternating current generator.

2. In a network calculating board, the combination of a network of impedances simulating the actual lines and loads of a power system, an alternating current generator connected to said network of impedances and determining the voltage and frequency in said network, and a plurality of negative impedance networks connected to said network of impedances and responsive to said voltage and frequency, said negative impedances taking current from the first said network in direction opposite to that of an ordinary impedance, thereby simulating the action of a real generator.

3. The combination of claim 2 in which the negative impedance networks are supplied with a source of unidirectional energizing potential.

GLENN W. BILLS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 555,301 Burke Feb. 25, 1896 1,837,851 Chisholm Dec. 22, 1931 1,994,457 Barnes 1, Mar. 19, 1935 2,197,239 Harrington u Apr. 16, 19 20 2,250,277 Schaper July 22, 1941 2,315,649 Parker Apr. 6, 1943 2,359,504 Baldwin V Oct. 3, 1944 2,488,740 Robert Mar. 16, 1945 

